1. Field of the Invention
The present invention relates to a reverse cycle refrigeration system. More specifically, the present invention relates to a multiple zone system having means for adjusting air flow rates to maintain a relatively constant discharge temperature regardless of the fluctuation in ambient conditions.
2. Description of the Prior Art
In a conventional vapor compression refrigeration circuit the compressor acts on refrigerant to raise its temperature and pressure. Refrigerant is then condensed from a gas to a liquid in a condenser giving off heat. This liquid then undergoes a pressure drop through an expansion device and is conducted to an evaporator where it changes state from a liquid to a gas absorbing heat during the phase change. This gaseous refrigerant is then conducted back to the compressor to complete the cycle.
In the heat pump application this refrigeration circuit is arranged with a reversing valve to change the direction of refrigerant flow through the circuit such that either of the two heat exchangers may act as a condenser or an evaporator. In a conventional circuit of this description, an indoor coil is located within the air flow path for the air of the enclosure to be conditioned and an outdoor coil is located in heat transfer relation with ambient air. During the heating season the indoor coil serves as a condenser such that gaseous refrigerant is condensed to a liquid refrigerant therein giving off heat to the indoor air in heat exchange relation with the indoor heat exchanger. During the cooling season, liquid refrigerant is evaporated to a gas in the indoor heat exchanger absorbing heat from the indoor air cooling same. The outdoor heat exchanger during heating season serves as an evaporator transferring heat energy from the outdoor ambient air to the refrigerant. During the cooling season, the outdoor heat exchanger is the condenser wherein the gaseous refrigerant is condensed to a liquid discharging heat energy to the ambient air.
Heat pump system operation is dependent upon several factors, one of which is the ambient air temperature to which heat energy is either absorbed or discharged. During the heating season, when heat energy is absorbed from the ambient air and transferred through the refrigeration circuit to the indoor air, the heating capacity and efficiency of the refrigeration circuit is dependent upon the ambient air temperature from which heat energy is absorbed. As the differential between the outdoor temperature and the indoor temperature increases the efficiency and capacity of the heat pump system generally decrease.
As a result of this decrease in efficiency as the outdoor temperature drops the refrigeration circuit is capable of supplying a reduced amount of heat energy to the indoor air. Consequently, with a constant volume flow rate the indoor air in heat exchange relation with the indoor heat exchanger as the outdoor ambient air temperature drops the temperature of the indoor air leaving the indoor heat exchanger will also decrease. This presents a possible annoyance for occupants of the enclosure in that the air being discharged to heat the enclosure may be at a sufficiently low temperature to feel cool although still having the capacity to supply substantial heat energy to the enclosure.
The herein invention has, as a part thereof, a temperature sensing device for ascertaining the temperature of the air being discharged from the indoor heat exchanger during heating operation. A fan driven by an electric motor is used to circulate air through the indoor heat exchanger. Means are provided for varying the speed of the fan in response to the temperature of the discharged air from the heat exchanger such that as the capacity of the refrigeration circuit decreases, the air flow volume rate through the heat exchanger may also be decreased to maintain the leaving air temperature from the indoor heat exchanger relatively level.
The description herein further details a two zone system wherein the primary zone is connected directly to the supply plenum for receiving air from the indoor heat exchanger and whereas the secondary zone plenum receives a regulated amount of air from the supply plenum. A damper is provided for regulating the volume of the air to the secondary zone. The damper is also positioned in response to the leaving air temperature from the indoor heat exchanger. Consequently, as the indoor fan speed is reduced reducing the volume of conditioned air being supplied to the enclosure the damper may be regulated to adjust the supply of air to the secondary zone. The primary zone is always supplied with a preselected volume flow rate of air by not reducing fan speed below a predetermined level and the damper is adjusted so that the remaining volume flow rate as determined by the fan speed is conducted to the secondary zone.